Removal of tin oxide from ores



y 1961 Y c. F. VHISKEY 2,982,610

REMOVAL OF TIN OXIDE FROM ORES Filed D80. 23, 1957 INVENTOR.

C/armce FJ /z'skey BY 7 v w ATTORNEY "United Stat Pflt rO REMOVAL OF TIN OXIDE FROM ORES Clarence F. Hiskey, Wallkill, N.Y., assignor to Transition Metals & Chemicals, Inc., Wallkill, N.Y., a corporation of Delaware Filed Dec. 23, 1957, Ser. No. 704,681

'5 Claims. (Cl. 23-98) Tin usually occurs in nature in the form of an oxide as in cassiterite, or in columbite. Sometimes tin occurs as a sulfide and the tin in sulfide mineral has been usually roasted t'o-convert it to the oxide prior to the usual extraction procedures.

But it has generally proved impossible to apply commercially ordinary methods of value recovery to tin ores carrying less than five percent of tin.

Moreover, tin is an objectionable impurity in some ores such as columbite ores, and has usually been separated from the accompanying metals after the whole of the values has been separated from the gangue of'the ore.

Thus the small percentage of tin in such ores as columbite ore has proved an expensive ingredient to deal with, even though the percentage of tin present has been small though seriously objectionable.

Other features and advantages will hereinafter appear.

The accompanying drawing shows diagrammatically in sectional side view, one form of apparatus for carrying out the present invention.

In this drawing, the crucible 1, takes the form of an eight inch iron pipe, five feet long closable at the top by a screwed on cap 2 provided with four quarter-inch vent holes 3, and closed at the bottom by a screwed on cap 4, having a bottom opening 5 into which is screwed a pipe 6 coming up through an opening 7 in the bottom 8 of the refractory jacket 9 which is spaced several inches away from the crucible 1.

The pipe 6 is adapted to convey to the interior of the crucible 1 vapors of dissociated ammonium chloride produced by heating a container 10 in a second refractory jacket 11, the heating element being diagrammatically shown as a looped pipe 12 lying in the space 3 between the container 10 and jacket 11.

A satisfactory container 10 was an ordinary empty nitrogen cylinder, and was readily filled by removing the connections 13 to the pipe including the closable valve 14, which is operable by a long rod 15 extending to outside the jacket 11.

The cap 4 is shown resting on a hollow refractory cylinder or layer of broken Slag 16 lying on the bottom 8 of the jacket 9 and carries within the crucible a porous ceramic support or layer of grog 17 covered by five or six layers of 200-mesh stainless steel screen 18 to support the charge in the crucible clear of the bottom.

The vent holes 3 permit gases and volatilized products 9 to rise beneath the removable cover 19 and pass off 7 through a conduit 20 in the central opening 21 in the cover 19 so they are carried through a cooling extension 22 of the conduit to the dust collector diagrammatically shown as a cyclone 23 where the gases pass 05 at 24.

, '2 The dust under the control of a'valve 25 falls into a can or bag 26. A Cottrell electrical precipitator may prove more satisfactory than the cyclone described above.

The crucible 1 is shown heated by combustible gases entering port 27 through the jacket 9.

In the process described in some detail below, -the tilt is volatilized largely as one or the other of its chlorides and it is found that the tin present is readily so volatilized selectively to the substantial exclusion of other metals even though the ore is comminuted only to moderate fineness. Q I

'For' example, columbite ore ground to pass a 20 mesh screen but held on a 40 mesh and carrying about 3% tin oxide. was treated with volatilized ammonium chloride to yield about the same result as the same ore ground to all pass a 200 mesh sieve, and the speed of the reaction was only slightly altered by the altered conditions resulting from varied fineness of grinding.

On the other hand, the reaction temperature and the' degree of contact between the mineral and the ammonium chloride gas have a profound effect on both the rate V and the completeness of the reaction.

For example, in the case of a columbite mineral c0ntaining about 3% tin oxide reaction at 500 C. for 24 hours with a space velocity (volume of gas per unit volume of ore per hour) of ten reduced the tin oxide to only 2.4%. Elevating the temperature to 600 C. and maintaining the reaction at the same space velocity for 5 hours reduced the tin oxide content to 0.25%. At 750 C. under similar conditions of space velocity the tin oxide content was reduced to 0.03% in about two hours.

In one run with the above described apparatus, the pipe 6 and its valve were disconnected fromthe container 10 and more than 2 pounds of granular ammonium chloride were'loaded into the container, the pipe 6 and its columbium pentoxide, 7.10% tantalum pentoxide, 1.72%

titanium dioxide, 1.64% stannic oxide, 2.03% manganous oxide and 18.33% ferrous oxide, and the crucible connected to the pipe 6 inside the jacket 9.

The crucible 1 was rapidly heated to a temperature of 750 C. by entering gases at port 27, and the valve 14 opened when the crucible contents reached that temperature. Thus the volatilized ammonium chloride was admitted through the pipe 6 at a temperature at least 338 C.

The volatilized ammonium chloride passed through the hot ore bed until two (2) pounds had passed through it such a rate that the operation took about three (3) hours. Heating then stopped.

The crucible 1 was cooled, the apparatus disassembled and the de-tinned ore removed from it. V

Assay of the thus treated ore showed the tin oxide content reduced to 0.05%.

It was found possible to treat the comminuted ore in a horizontal tubular tray with the volatilized ammonium chloride, but unagitated ore thus treated showed a diminution in the completeness of de-tinning. Thus as the depth of the mineral bed was varied in a horizontal tubular reactor, it was observed that the tin content at the bottom of the tray was greater the greater the depth for aazuu 7 3 and that NH becomes a reducing gas as follows:

2NH3 N2+3H2 SnO +H; SnO.+H O

Where no attempt is made to recover tin chlorides, the ore may be heated in an indirectly heated rotating horizontal kiln, closed to air except where the ammonium chloride vapors enter and leave.

The ore may be heated in a crucible pot having a loose cover, and the ammonium chloride vapors passed down through the ore bed to a dififusing elementat the bottom of the crucible, so the vapors pass upward through the ground ore and out of the crucible pot.

Iron, stainless steel and ceramics have all been found satisfactory materials for constructing the device.

Temperatures up to 800 C. also proved useful.

It seems as if the ammonium chloride reacted interfacially with the tin oxide, converting the oxide partly into stannous chloride and partly into stannic chloride, and the heat boiled off these chlorides.

Having thus described certain embodiments of the invention in some detail, what is claimed is:

l. The process of removing tin from a columbite ore containing less than 5% by weight of cassiterite, which consists in separately heating ammonium chloride to dissociate it into ammonia gas and hydrogen chloride gas and then passing the dissociated gases through a mass of said ore separately heated to a temperature at which the ammonia gas will crack into nitrogen and hydrogen to volatilize stannous chloride.

2. The process of removing tin from a columbite ore containing tin sulfide which consists in converting the sulfide to an oxide and heating ammonium chloride to crack it into ammonia gas and hydrogen chloride gas and passing the cracked ammonium chloride gases through a mass of the comminuted ore at a temperature suflicient to volatilize stannous chloride.

3. The process of removing tin from a columbite ore containing it in form of cassiterite, which consists in heating ammonium chloride in a container to above 338 C. to dissociate it to ammonia gas and HCl gas, heating the comminuted ore to above 700 C., and pressing the heated and dissociated ammonium chloride vapors through the heated ore to crack the ammonia gas into nitrogen and hydrogen.

4. The process of recovering tin from a columbite ore containing it which consists in heating ammonium chloride in a container to above 338 C., heating the comminuted ore to above 700 C., and passing the heated ammonium chloride vapors through the heated ore and chilling and collecting the volatilized tin chloride.

5. A process for removing tin oxide from columbite ore by volatilization as the chloride by means of passing a stream of ammonium chloride gas preheated above 338' C. in contact with a bed of said ore preheated at a temperature over 500 C.

References Cited in the file of this patent UNITED STATES PATENTS 1,822,266 Becket Sept. 8, 1931 1,843,060 Ashcroft Jan. 26, 1932 2,345,210 Muskat Mar. 28, 1944 FOREIGN PATENTS 276,743 Great Britain Sept. 2, 1927 

1. THE PROCESS OF REMOVING TIN FROM A COLUMBITE ORE CONTAINING LESS THAN 5% BY WEIGHT OF CASSITERITE, WHICH CONSISTS IN SEPARATELY HEATING AMMONIUM CHLORIDE TO DISSOCIATE IT INTO AMMONIA GAS AND HYDROGEN CHLORIDE GAS AND THEN PASSING THE DISSOCIATED GASES THROUGH A MASS OF SAID ORE SEPARATELY HEATED TO A TEMPERATURE AT WHICH THE AMMONIA GAS WILL CRACK INTO NITROGEN AND HYDROGEN TO VOLATILIZE STANNOUS CHLORIDE.
 2. THE PROCESS OF REMOVING TIN FROM A COLUMBITE ORE CONTAINING TIN SULFIDE WHICH CONSISTS IN CONVERTING THE SULFIDE TO AN OXIDE AND HEATING AMMONIUM CHLORIDE TO CRACK IT INTO AMMONIA GAS AND HYDROGEN CHLORIDE GAS AND PASSING THE CRACKED AMMONIUM CHLORIDE GASES THROUGH A MASS OF THE COMMINUTED ORE AT A TEMPERATURE SUFFICIENT TO VOLATILIZE STANNOUS CHLORIDE. 